Applicants claim priority under 35 U.S.C. xc2xa7119 of Russian Application No. 200104952 filed on Mar. 1, 2000. Applicants also claim priority under 35 U.S.C. xc2xa7365 of PCT/RU01/00081 filed on Feb. 26, 2001. The international application under PCT article 21(2) was not published in English.
This invention relates to hydrodynamics and can be used for deep boreholes drilling, opening the productive rocks, rock treatment to create channels for fluid flowing, dispersing solid particles into liquid or mixing insoluble liquids, pipes cleaning.
Devices are known to produce regime of cavitating flow due to placing at the outlet of a nozzle of an obstacle for the flow of liquid (xe2x80x9cOil and Gas J.xe2x80x9d, 1977, 31/X, vol. 75, no. 45, pp. 129-146). Channel of the nozzle can be of any configuration: a narrowing one toward the nozzle exit (U.S. Pat. No. 4,378,853, publ. Apr. 5, 1983) or broadening one toward the nozzle exit (U.S. Pat. No. 5,897,062, publ. Apr. 27, 1999), one in the form of a Laval nozzle (U.S. Pat. No. 4,187,921, publ. Feb. 12, 1980), and where the obstacle can be made in a form of a rigidly fixed bar, transverse beam, curved blade, cylindrical funnel (xe2x80x9cOil and Gas J.xe2x80x9d, 1977, 31/X, vol. 75, no. 45, pp. 129-146), or projections into the inner space of the channel (U.S. Pat. No. 4,262,757, publ. Apr. 21, 1981).
These devices can be considered as prior art analogs in respect to the proposed invention. Main shortcomings of these devices are as follows:
1) at velocities of a liquid flow required to obtain cavitation at nozzle exit the high pressure drop takes place on the nozzle, what can be provided not in every case, especially in deep wells;
2) at high values of hydrostatic pressure, e.g. in deep wells, obtaining of cavitation using such devices is problematic.
A device is known (U.S. Pat. No. 4,511,254, publ. Nov. 10, 1981) proposing a cavitating nozzle in a drill bit. The cavitating nozzle comprises a casing body with shaped channel for flowing of a liquid and an obstacle placed into the flow. By combination of features this device is a closest prototype to the proposed invention.
Main shortcomings of this prototype are as follows:
1) high losses of hydraulic power to obtain cavitation at the nozzle exit;
2) when using a unmovable bar placed into the flow, no separation of cavitational cavity occurs and therefore cavitational effecting on a bottom hole, which is apart from the nozzle, is inefficient;
3) at high values of hydrostatic pressure in deep wells it is impossible to obtain cavitation using such devices.
The proposed cavitating nozzle comprises a casing body with a shaped channel for passing of a flow of liquid and an obstacle placed in the flow which obstacle is made movable in radial direction. The inner space of the nozzle can be splitted along axial direction of it by a baffle into two chambers, where the said movable obstacle, when it is in its ultimate position, closes the cross-section of one of the chambers. The obstacle can be made in the form of a ball or cylinder and to have one or more degrees of freedom of radial motion and it closes the total cross-section of the channel by not less than 80%.
Nature of features distinguishing the uniqueness of the proposed invention can be explained by the following: the obstacle that is movable in radial direction appears to be a hydrodynamic cavitator which induces separation of the decompression zone (cavitational cavity). If the obstacle in unmovable (regardless its particular design) it doesn""t occur. Additionally, the cavitator made in the form of a ball or cylinder, have no equilibrium position and it automatically shifts either to ultimate right or left position as hydrodynamic pressure changes in the clearance between the cavitator and wall of the channel. In its ultimate position the cavitator closes one of the chambers formed by the baffle and thus performs a function of a valve. It allows in conditions of high hydrostatic pressure in deep wells to use kinetic energy of liquid to rupture its continuity. The movable obstacle closes the total cross-section of the channel by not less than 80%. It is determined by that at lower dimensions of cavitator it is impossible to obtain velocities of the liquid flow in the clearance between the cavitator and wall of the channel that are sufficient to produce cavitational cavities at practically available pumping rates of drill pumps.